Food provides

1. Energy (Calorie = amount of heat required to raise the temperature of one kilogram of water by one degree at one atmosphere pressure)

2. Materials to build body (carbon, proteins, minerals, lipids, etc.)

Humans need a variety of foods to supply their nutritional needs

Carbohydrates

Proteins

Fats

Vitamins

Minerals

The Food Pyramid

is a guide for what we

should eat daily.

Malnutrition – a condition when a person does not consume enough calories or nutrients to supply the body’s needs

Marasmus (“wasting away”)– not enough calories and protein

Kwashiorkor (“displaced child”) – severe protein deficiency, bloated belly, can cause mental retardation

Overnutrition – too many calories, results in health problems including diabetes, heart disease, stroke

How do we supply 6.8 billion people with enough food?

Agriculture = practice of

raising crops and livestock for

human use and consumption

•Cropland = land used to

raise plants for human use

•Rangeland or pasture = land

used for grazing livestock

Land devoted to agriculture

covers 38% of Earth’s land

surface

Agriculture was invented independently by different cultures

The earliest plant and animal domestication is from the “Fertile Crescent” of the Middle East

Wheat, barley, rye, peas, lentils, onions, goats, sheep

Traditional agriculture = biologically powered agriculture, using human and animal muscle power

Subsistence agriculture = families produce only enough food for themselves

Uses animals, irrigation and fertilizer, but not fossil fuels

Industrialized agriculture = using large-scale mechanization and fossil fuels to boost yields

Yield = amount of food that can be produced in a certain area Also uses pesticides, irrigation and fertilizers

Monocultures = uniform planting of a single crop

Why might monocultures be a bad idea?

Monoculture = a large expanse of a single crop

More efficient, increases output

Devastates biodiversity

Susceptible to disease and pests

Narrows human diet: 90% of our food comes from 15 crop species and 8 livestock species

Armyworms easily defoliate monocultures

The Green Revolution

Use of new varieties of crops dramatically increased per-acre yields

Spread to the developing world in the 1940s with wheat, rice, corn

Depended on large amounts of Synthetic fertilizers

Chemical pesticides

Irrigation

Heavy equipment

Soil is a thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms, most of them microscopic decomposers

Soil is important because: 1. It provides most of the

nutrients needed for plant growth, and subsequently consumer growth.

2. It is the primary filter that cleanses water as it passes through.

3. It is a major component of the earth’s water recycling and water storage processes.

Components of soil 25% air (mostly N and O)

25% water

45% mineral

5% organic matter

Amounts of air and

water vary

Soil is a renewable resource Formation of soil depends on 5 factors:

1. climate 3. biologic activity 5. time

2. terrain 4. geology

It takes 15 to 100s of years to form one cm of soil!

*Parent material = the base geologic material of soil

**Bedrock = the continuous mass of solid rock comprising the Earth’s crust

*

**

Weathering produces soil Weathering = the physical,

chemical, or biological

processes that break down

rocks to form soil

Physical (mechanical)

•wind and rain

•no chemical changes in

the parent material

Chemical

•substances chemically

interact with parent

material

Biological

•organisms break down

parent material

Soil Horizons: Layers of mature soil O horizon – organic material, leaf

litter, many organisms live here

A horizon – topsoil layer, zone of accumulation of organic matter and nutrients

These top 2 horizons contain:

- the roots of most plants

- billions of living things (bacteria, fungi, earthworms, insects, etc.)

Soil Horizons: Layers of mature soil B horizon – subsoil, accumulates iron,

clay, aluminum and organic compounds that leach down from above

(leaching: process in which water seeps down through open spaces or pores in soil, dissolving minerals and organic matter and carrying them to lower layers)

Soil Horizons: Layers of mature soil C horizon – parent material, contains

large lumps or shelves of rock

R horizon (under C horizon)- bedrock

Soil Particles Three types, based on size:

1. Sand: 2.0-0.05 mm

2. Silt: 0.05-0.002mm

3. Clay: less than 0.002mm

Relative amounts determine soil texture

Soil Textural Classification

Soil Permeability Definition: the rate at which water and air move from upper to

lower soil layers

The more spaces there are between soil particles, the more permeable it is

Plants need good drainage, but not too much

Plants are like Goldilocks Sandy soil: This soil is too permeable – water runs right

through

Clay soil: This soil is too impermeable – water can’t get through

Loam: This soil is just right! (mixture of sand and clay)

Which is which?

Sand on left

Loam in middle

Clay on right

Other soil characteristics that are important to plants

Nutrient content – nitrogen, phosphorus and potassium

pH – if soil is too acidic or basic, plants can’t grow

Agriculture and Population Growth The earth has a carrying capacity for the human

population – we don’t know what it is.

We do not have unlimited land and resources to produce food for people.

We face food issues as our population grows:

1. Lack of enough arable land

Graph showing per capita arable land over time:

2. Soil degradation soil erosion – the dislodging and movement of soil by

wind or water, occurs when vegetation is absent

Erosion increases through: excessive tilling, overgrazing, and clearing forests

Can result in desertification - most prone areas are arid and semiarid lands

The Dust Bowl

In the late 19th and early 20th centuries, settlers arrived in Oklahoma, Texas, Kansas, New Mexico and Colorado

Grew wheat, grazed cattle

Removed vegetation

A drought in the 1930s made conditions worse

Thousands of farmers left their land and had to rely on governmental help

Various types of soil erosion

Splash

Sheet

Rill

Gully

We lose 5-7 million ha (12-17 million acres) of productive cropland annually

3. Uneven food distribution around the world

Developing countries: usually faster population growth, more poverty, less infrastructure to grow and distribute food

4. Problems with irrigation

Irrigation = Artificially providing water to support agriculture

Unproductive regions become farmland

Waterlogging = over-irrigated soils Water suffocates roots

Salinization = the buildup of salts in surface soil layers

Depletion of ground and surface waters

5. Loss of biodiversity When we convert natural habitats to farms, we reduce

natural habitat

We also plant monocultures and use few species for crops

6. Negative effects of overgrazing

Soil compaction

Non-native invasive species invade

Less palatable to livestock

Out compete native vegetation

Ungrazed plot Grazed plot

7. Pollution from: Agriculture - pesticides, herbicides, fertilizers,

Livestock (on feedlots) – animal waste, excess methane is a greenhouse gas

Overapplication of Fertilizer Inorganic fertilizer use has

skyrocketed

Overapplying fertilizer can ruin the soil and severely pollute several areas

Runoff causes eutrophication in nearby water systems

Nitrates leach through soil and contaminate groundwater

Nitrates can also volatilize (evaporate) into the air

8. Resistance to pesticides Some individuals are genetically immune to a pesticide

They survive and pass these genes to their offspring

Pesticides stop being effective

Evolutionary arms race: chemists increase chemical toxicity to compete with resistant pests

Solutions to our agriculture issues:

Sustainable Agriculture Industrial agriculture may seem necessary, but less-intensive

agricultural methods may be better in the long run

Sustainable agriculture = does not deplete soil, pollute water, or decrease genetic diversity

Protecting soil: crop rotation and contour farming

Crop Rotation = alternating the crops grown field from one season or year to the next,

Cover crops protect soil when main crops aren’t planted

Wheat or corn and soybeans

Contour Farming = plowing furrows sideways across a hillside, perpendicular to its slope, to prevent rills and gullies

Protecting soil: terracing and intercropping

Terracing = level platforms are cut into steep hillsides, sometimes with raised edges A “staircase” to contain water

Intercropping = planting different types of crops in alternating bands or other spatially mixed arrangements Increases ground cover

Pros and cons of no-till farming Almost half of U.S. farmland

uses no-till farming

Benefits: reduced soil erosion, greater crop yields, enhanced soils

Negatives: increased use of herbicides and fertilizers

Biological control

Biological control (Biocontrol) = uses a pest’s natural predators to control the pest Reduces pest populations

without chemicals

Cactus moths control prickly pear

Bacillus thuringiensis (Bt) = soil bacteria that kills many pests

Salinization prevention

It is easier and cheaper to prevent salinization than fix it

Do not plant water-guzzling crops in sensitive areas

Irrigate with low-salt water

Irrigate efficiently, supplying only water that the crop requires

Drip irrigation targets water directly to plants

Integrated Pest Management (IPM)

IPM uses multiple techniques to suppress pests

Biocontrol

Chemicals, when necessary

Population monitoring

Habitat alteration

Crop rotation and transgenic crops

Alternative tillage methods

Mechanical pest removal

Within 4 years of using IPM in Indonesia, rice yields rose 13%, and

$179 million saved by phasing out subsidies

Genetically Modified Organisms (GMOs)

Genetic engineering = laboratory manipulation of genetic material

Genetically modified organisms = organisms that have been genetically engineered by …

Recombinant DNA = DNA created from multiple organisms

Genetic engineering has both benefits and risks Benefits of genetic engineering:

Increased nutritional content

Increased agricultural efficiency

Rapid growth

Disease and pest resistance

Negatives of genetic engineering: Risks are not yet defined or well understood

Protests from environmental activists, small farmers, and consumer advocates

Some genetically modified foods

Change diet practices Eat less meat

Eat organic

Eat locally produced foods

Eat diverse foods

Eating animal products has significant impacts As wealth and commerce increase, so does consumption of meat,

milk, and eggs

Global meat production has increased fivefold

Per capita meat consumption has doubled

Domestic animal production for food increased from 7.3

billion in 1961 to 20.6 billion in 2000

Energy choices through food choices 90% of energy is lost every time

energy moves from one trophic level to the next

The lower on the food chain from which we take our food sources, the more people the Earth can support.

Some animals convert grain

into meat more efficiently than others

Environmental ramifications of eating meat Land and water are needed to raise food for livestock

Producing eggs and chicken meat requires the least space and water Producing beef requires the most

When we choose what to eat, we also choose how we use resources

Organic agriculture

Organic agriculture = Uses no synthetic fertilizers, insecticides, fungicides, or herbicides Relies on biological approaches (composting and biocontrol)

People debate the meaning of the word “organic”

Organic Food Production Act (1990) establishes national standards for organic products

The USDA issued criteria in 2000 by which food could be labeled organic

Aquaculture

World fish populations are plummeting Technology and increased

demand

Aquaculture = raising aquatic organisms for food in a controlled environment Aquatic species are raised in

open-water pens or land-based ponds

The benefits and drawbacks of aquaculture

Benefits: A reliable protein source

Sustainable

Reduces fishing pressure on overharvested wild fish stocks

Energy efficient

Drawbacks: Diseases can occur, requiring

expensive antibiotics

Large amounts of waste

Farmed fish may escape and introduce disease into the wild

Government intervention The Soil Conservation Service

Started in 1935, the Service works with farmers to develop conservation plans for farms Assess the land

Prepare an integrated plan

Work closely with landowners

Implement conservation measures

Conservation districts = districts operate with federal direction, authorization, and funding, but are organized by the states

What can you do?

Eating to Save the Earth: Food Choices for a Healthy Planet by Linda Riebel and Ken Jacobsen

As a consumer, you can:

Use locally grown food, or grow your own! – uses less fuel for transportation

(Example: a single fast food meal comes from Texas (meat), Nebraska (corn to feed cow), Washington (cheese), California (lettuce and tomato), Idaho (wheat for bun and potatoes), Louisiana (salt), Pennsylvania (ketchup), Ohio (ketchup pouches), Arkansas (french fry box), Iowa (corn syrup for soft drink))

Buy organic – few or no pesticides or chemicals added

Go vegetarian (or nearly) – use little or no meat, dairy, eggs

Use less processed foods - stay close to the food’s natural state

Buy products with less packaging

Branch out and buy unusual products to support diversity

Consider purchasing products that support fair trade

Try not to waste food

Educate yourself and think critically

http://well.blogs.nytimes.com/2007/10/22/five-easy-ways-to-go-organic/?em&ex=1193544000&en=39941565969220ef&ei=5087%0A